A chronic total occlusion (CTO) is an arterial vessel blockage that prevents blood flow beyond the obstruction. CTO's typically occur in coronary, peripheral, pediatric, and either small arteries. In the coronary and peripheral arteries, they result from the same underlying cause—atherosclerosis.
Endovascular therapies for arteries below the knee have emerged as a promising revascularization technique for patients with critical limb ischemia (CLI). However, when employing standard angioplasty techniques, angioplasty of BTK arteries fails to achieve revascularization in up to 20% of cases. The main cause for failure is the inability to penetrate the plaque's proximal cap with the guidewire.
A new technique of approaching the plaque from below—known as the retrograde approach—is often used to pass the guidewire through the plaque from the other direction. This approach has high success rates, but is technically challenging to perform and has its own complications, especially the danger of vessel perforation.
In order to use the retrograde technique, the clinician must puncture the small target artery with a needle—usually smaller than a 21 gauge needle. The clinician relies on several angiographic images to aim the needle into the artery, and verifies proper needle tip location by observing blood flow exiting from the needle's proximal end.
Puncturing small arteries is not easy; it requires proper manipulation of the C-arm and a gentle needle stick to avoid arterial perforation. Once a guidewire is inserted (through a small sheath or directly (sheath-less) through the skin) within the needle into the artery, the needle can be removed.
Currently, relative short standard needles are used to puncture small blood vessels. Long needles that might potentially extend the user hand from the puncturing site are not used for two reasons:
1) Long thin needles are too flexible, which prevents accurate and controlled positioning of the needle tip in the direction of the blood vessel; and
2) Blood is expected to come out from the proximal end of the needle. This is fine for a short needle, but for a long needle the blood may not reach the proximal end due to low blood pressure in the treated vessel and high flow resistance of the long narrow needle lumen.
Another important disadvantage of the prior art, is that during this needle insertion the clinician's hand is exposed to direct X-ray radiation which may have deleterious long-term health effects.